Building a germanium fuzz face guitar pedal

Rock in the new year with a guitar pedal you built yourself. [Doug Kovach] took the time to share his project with us in the video after the break. He starts with a bit of history of the artists that have used fuzz pedals similar to this one. It seems great guitarists have been hacking since way back. [Doug’s] rendition uses the warm sounds of germanium transistors in a design that produces professional results. But if you need something a little bit less serious try the stomp-box.

Hi George, this photo is with the first circuitboard which was later replaced. One of the batteries was also removed and an external power source was hooked up to the power supply connector. Since the pedal uses a positive ground I left this till last to hook up so as to make sure the circuit worked correctly before getting into the weird power supply circuit.

The write up is a bit confusing. This pedal is a combination of the Dallas Arbiter Fuzz Face and the Colorsound MKII Tonebender. There is no equivalent pedal on the market and there never has been. To the best of my knowlege I am the only one to create such a device. While Jimi Hendrix certainly had his pedal modified as did Jimmy Page neither of them went to this extent. Jimi Hendrix was a bit of a hacker but relied on Roger Mayer to do the dirty work and soldering for him, Jimmy Page was not. He simply heard sounds and asked others to make them for him.

The photos are posted on Facebook and the video is on Youtube. I realize the implications of using Facebook to host my photos with but since there is nothing really proprietary going on here I am good with that. This is the public link to the photo set. You do not need to be a member of Facebook to view them. I have chosen to use Facebook to host them because with Facebook I can control who can see them and whether or not I want them public or private.

Tim, the circuit uses 3 AC128K milspec Germanium Transistors. there are no opamps in the circuit. I used chip sockets as I explained in the video to prevent having to solder the transistors but this did not work out and the entire board was scrapped and replaced and the transistors soldered into place on the new board.

I wasn’t criticizing the choice, Doug, I asked because I’m interested too in publishing some ideas one day but Instructables is terrible and Facebook raises some concerns. This project is nothing new as you wrote, but what if it was?

I’m thinking about putting the interesting stuff off Facebook and posting only a link on it. Does any expert know if it would be enough to prevent Zuckerberg profit from my work?
What if the material/media is released under Creative Commons and the software under GPL licenses? Would that invalidate any attempt by FB to profit exclusively from it?

No problem qwerty. I have done a small amount of research and photobucket and flickr and their ilk are always public all the time and have even more draconian statements about IP becoming theirs if I use their services. If I wanted to retain IP of my materials I would publish them on a website of my own. This is why I have not posted the schematic yet.

I am undecided on whether or not I want to release it. What I did was not hard to figure out but I did hafta figure out a lot of other things in order to make it work properly and play well with other devices. What do you guys think?

@zool your correct it used the NKT275 PNP transistors. The MKII Tonebender used the AC128 PNPs. I was originally using OC75 PNPs. The problem with all of these is gain drift as I stated in the video. Here in Arizona the summer temps get quite high and so render these transistors useless. This is why in the video I stated that I switched to the AC128k transistors. They have an aluminum heatsink and can withstand temps up to 500 degrees F with no gain drift. The rest of the specs are similar if not exact with another diffeerence and that being voltages of operation. the AC128K can withstand voltages up to 32 volts. So this has me thinking about doubling the supply voltages or even tripling them to 28 volts. This of course brings subsequent problems with sound. At higher voltages the sound will be cleaner thereby negating the fuzz distortion which is the reason behind all of this. Who knows though. This may be the start of a new type of overdrive pedal! Germanium overdrive a la Jimi or Jimmy anyone?

Ok here is what I have decided to do. Since I do value the amount of discovery and engineering I have put together to create this pedal I will simply post links to each of the schematics and articles I referenced during its creation and engineering.

Now… The Colorsound MKII Professional Tonebender circuit: Be warned this is a beastly fuzz pedal. The circuit is not to complicated since it is only one gain stage more than a typical Fuzz Face added to the front of the Fuzz Face circuit. You may find information about the MKII Tonebender here:http://fuzzcentral.ssguitar.com/mkII.php

And here is the specific schematic I used:

You will note there are many variants of each schematic and pedal. I specifically chose the earliest versions of each pedal to work with simply because these are the ones using the Germanium Transistors. Later versions of both of these pedals switched to Silicon Transistors which changed the sound. Some people prefer the sound of Germanium over Silicon and vice versa. Some folks even like to mix and match and you will encounter many such circuits on the WWW.

The problems with these types of pedals are their strange POSITIVE ground power supply (on earlier models) and transistor gain drift with temperature (also on earlier models). Later models switched to Silicon for stability and consistency not to mention being much cheaper. Transistor biasing can affect the sound and sonic tone of these pedals and you can certainly hear differences between a good or bad biasing of the transistors. The way I recommend to build the circuit is on breadboard so you can swap out biasing resistors to fine tune the circuit to your particular transistors and their specific gain structures. Take my word for it. It will be much easier to do on breadboard then after you have already soldered the board together. There are several locations to acquire Germanium Transistors. Steve Daniels over at http://www.smallbearelec.com provides both gain tested and pre-biased transistors and resistors sets. He also provides non-tested transistors for a few bucks less but you must measure and test each transistor to find its gain and biasing resistor amounts etc… Or not! The companies that built these pedals did no such thing. They simply built pedals using the next part grabbed out of a bucket of parts. So with that said the tone is completely up to you.. Its your pedal so build it so it sounds amazing to you and that is good enough!

Can someone explain the use of germanium transistors vs a similarly spec’d silicon transistor?
I’ve heard countless people say they have a ‘warmer’ or ‘more clean’ sound to them, but what does that mean electrically? Isn’t there a simple way to replicate that sound without germanium transistors?

@Spork… First let me say that “Tone” is subjective and varies from person to person.

To answer a few of your questions. As I have stated silicon transistors are much more stable then GE trannies due to heat instabilities. In order to substitute SI trannies for GE trannies the circuit must be re-biased to closer match the specs needed by the SI trannies. This means added resistors and caps to stabilize the circuit so the SI transistors can work correctly. Electrically this means different impedances and voltages. It means different gain structures and different ripple filters as compared to the original GE circuits. They just sound different. As for emulating the sound of the GE trannies this might be feasible through DSP but I would not count on getting it to sound the same. At least no more than emulating the sound of tubes versus solid state sounds realistic. To really understand this you would require an answer discussing atomic structure and physics.

@Spork: besides being generally worse stability-wise than silicon transistors, as Doug pointed out, generally germanium transistors also have a limited bandwidth so they gracefully cut the higher part of the audio spectrum which gives their less harsh sound compared to silicons when it comes to distorion (we’re not talking about HiFi where silicons outperform germaniums in every aspect).

This can be _somewhat_ emulated with silicon transistors by adding a small capacitor (a few hundred pF max) between base and collector of each transistor. A resistive trimmer in series with the capacitor can help to damp the high frequencies to the amount of your choice.
Don’t expect this trick to make silicons sound exactly as germaniums but for some people could be enough.

@Doug and qwerty
Thanks for the responses. I wouldn’t go as far as DSP, because I may as well have used that from the get go.

qwerty, that was my thought exactly, I was wondering if I could use a high pass filter to mimic the smaller bandwidth of the germanium transistors.
I’m assuming this little trick will be enough for me as I’m a fair bit deaf.

It seems as though I will hopefully be manufacturing a couple of productions runs of the updated version of this pedal. Same specs and transistors and mostly the same circuit but 4 modes of operation as opposed to the 3 modes this pedal has. By the way the owner of this pedal still loves it and uses it everyday both on stage and in the studio. I also constructed his custom designed 100 watt tube amp as well as the channel switching device. He has had no problems at all in the past 4 years with any of them. The only things in his rig I did not make were the guitar and the cords and the pick. I have made two more of these pedals and they sold right away. I barely had time to finish them because they were so eager to use them. The creamy lusciousness of the germanium allows full chords as well as single notes unlike a lot of modern distortion devices. I will make an announcement on this thread when the new pedals are available for sale if anyone is interested. I have not had the time nor the place to do any electronics work in the past few years due to life and medical problems but now I am back to stable again so look for new devices again soon! My website is http://www.duoglassix.com if I am allowed to post a link outside of hack a day. My YouTube channel is also DuoGlassix.